Polymerized alpha-mono-olefins stabilized with 2-tert. butyl-4-higher alkoxyphenols



United States POLYMERIZED a-MONO-OLEFINS STABILIZED WITH Z-TERT. BUTYL-l-HIGHER ALKOXY- PHENOLS Clarence E. Tholstrup and Alan Bell, Kingsport, Tenn, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Sept. 19, 1957, Set. No. 684,865

' 7 Claims. or. 260-4595 wherein n is an integer of from 10 to 20 and R represents an alkyl radical containing from 1 to carbon atoms.

The prior art is replete with disclosures as to the use of 2 or 3-te1t. butyl-4-methoxyphenol (known commercially as butylated hydroxyanisole or BHA) as an antioxidant or stabilizer for compositions subject to oxidative deterioration. However, none of this art teaches that the use of homologs of BHA is significantly superior to BHA itself. In fact the art usually indicates that BHA is the preferred compound. Moreover, experimental data derived from testing various homologs of BHA shows that there is usually little to be gained and ordinarily something worthwhile is lost in the use of various homologs related to BHA; e.g., see data in US. Patent 2,310,710. Although BHA has met with considerable commercial success as a stabilizer for various substrates it has no out standing properties in polymerized u-mono-olefins. Other stabilizers used in polyethylene, polypropylene and the like have not been fully. satisfactory for all purposes, particularly as regards thermal oxidative degradation.

It was quite unobvious to find that certain rather high homologs of BHA were quite effective to a surprisingly worthwhile degree in stabilizing polyethylene in particular and also other polymerized a-mono-olefins.

It is an object of this invention to provide stabilized compositions of matter normally subject to oxidative deterioration.

It is a further object to provide polymerized a-monoolefins, especially polyethylene, which have excellent stability under conditions conducive to oxidative degradation.

It is another object to provide hot plastic compositions including polyethylene, polypropylene or the like, especially polyethylene, which are reasonably stable and can be extruded into fibers, into sheets, onto wire, or coated onto fabric, paper,'metal, or otherwise fabricated into 2,983,710 Patented May 9, 1961 OH OH /CH: CQR Cm .4.

wherein n is an integer of from 10 to 20 and R represents an alkyl radical containing from 1 to 5 carbon atoms.

These plastic compositions can advantageously contain other components as may be desired from a consideration of the end use. Thus, mixtures of polyethylene and parafiin wax may be used for coating paper. Moreover, the particular higher homologs of BHA covered by this invention can be used alone or together with other antioxidants in paraffin wax containing little or no polyethyl ene or other polymerized a-mono-olefin; however, the results are not of anywhere near the same order as can be achieved according to this invention. In fact, it will become apparent from the data below that polyethylene is peculiar in its great receptivity to thermal stabilization by the compounds described herein. Although there is also considerable receptivity to such stabilization on the part of other poly-a-mono-olefins such as polypropylene, etc., the unusually good results regarding stabilization of polyethylene show that the stabilized polyethylene of this invention stands apart as being without an equivalent in the art. The preferred stabilizers of this invention are illustrated in the tables given below. The tertiary alkyl group is preferably in the 2-position and can advantageously be either a tert.butyl or a tert.octyl radical; however itcan also be tert.amyl,'tert.hexyl, etc. The CnH radical can be either a straight chain alkyl radical or a branched chain alkyl radical. The value of n can be a little below or above the range specified but the stabilizer characteristics even when n is 10 are quite inferior to the character istics in the especially preferred range where n is from 12 to 18.

The polymerized a-monoolefi-ns which can be eifectively stabilized by this invention are normally solid polymers such as polyethylene, polypropylene, poly-3-methylbutene-l, poly-3,3-dimethylbutene-l, polypentene-l, poly- 4-methylpentene-1, poly-4,4-dimethylpentene-land other homologous polymers including various mixtures and some copolymers. Howevers, this invention does not contemplate the stabilization of synthetic rubber which may include copolymers of a-monoolefins. This invention applies to solid polymers of ethylene and the isotactic and syndiotactic polymers of the other or: mono-olefins including isotacn'c polystyrene. This invention is not intended to cover the atactic polymers such as elastomeric copolymers of isobutylene produced by peroxide catalyzed polymerization techniques. As mentioned above, polyethylene is especially receptive to the stabilizing action of the stabilizers covered by this invention.

In a common process of extruding molten polyethylbra-nu apoiymeri tare? employed might 2b abliie v i'zuireazsed rapidity in: the: processing operation costi :of operations at be substantially ,.P PY 1 larly sensitive to oxidative breakdown occurring in processing or use.

Other matters relating to the stabilization of poly-mmono-olefins are set forth in greater detail in a copending application filed July 8, 1957 by Tholstrup and Tambyln, Ser. No. 670,375, wherein similar results are discussed involving the use of zinc or possibly cadmium diallcyldithiocarbarnates as stabilizers against thermal degradation,

l Although the stabilizers of the present invention can be used in amounts below about 0.001% or higher than about 5% by weight, it is generally advantageous to use them in amounts of from about 0.1% to about 2% by weight. Additional antioxidants or synergistic compounds can also be present which may further enhance the stability of the poly-a-mono-olefin against various degradative effects, e.g. propyl gallate, dodecyl gallate, octadecyl gallate, 2.G-ditert.butyl-4-methylphenol, zinc dibutyldithiocarbamate, and/or any of the known stabilizers for polymers of e-mono-olefins.

In order to further illustrate this invention various examples are presented such as in the tables set forth below. A thermal stability test has been developed to serve as an accelerated procedure to measure the storage life of poly-a-mono-olefins such as polyethylene at an elevated temperature. The oven life of the stabilized polymer is expressed in the tables below as thenumber of hours at 140 C. before the peroxide build-up takes place in the sample being tested. The details of this procedure as it is applied to polyethylene or the other polymers such as polypropylene can be described as follows wherein the stabilizers of this invention are referred raises :ptates at present and making 5 i e 1 l. X 0.002X 1000 Upon completion 'of this test, the oven life thermal stability is measured as the number of hours before peroxides are first observed.

During the oven storage test of polyethylene samples three visual observations should be made: (1) the color of the polyethylene samples both before and during the test: (2) the viscosity breakdown, that is, the ability of the samples to contain themselves rather than to continually spread out as a thin film on the watchglasses: and (3) the solubility of the polyethylene samples in carbon tetrachloride during the peroxide test. These properties are particularly important since viscosity breakdown and poor solubility in carbontetrachlorlde indicate that the initial start of peroxide build-up has been passed. When this occurs the peroxide value is usually low, because of the conversion to acids and other oxidation products.

Using the oven stability test described above, samples of various polymerized e-mon'o-olefins were tested and results are presented in the following tables:

TABLE I Antioxidant used in the amountof 1% Color during Oven Life,

by weight in Polyethylene Oven Test Hrs. at

Control (no antioxidant) good 7 BRA V fair :1 2tert.butyl-4-decyloxyphenoL t good 2-tert.butyl-4-dodecy1oxynhennl o 7 280 ?-tert.butyl-t-tetradecyloxyphenol; r 200 2tert.butyl-&octadecyloxyphenol V 0 166 Similar results were obtained using 2-tert.octyl-4-dodecyloxyphenol.

Similar results were obtained in regard to other polymerized a-mono-olefins and other stabilizers covered by the above description.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A stabilized composition of matter normally subject to thermal oxidative degradation consisting of a normally solid polymer selected from the group consisting of polyethylene and polypropylene and from about 0.001% to about 3% by weight of a stabilizer selected m from the group consisting of those compounds having the following formulas:

(311:! C- CHa CH; 0 cm '0 CH3 v n infl (En-Hana wherein n is an integer of from 12 to 18, inclusive.

2. A stabilized composition as defined in claim 1 wherein the polymer is polyethylene and the stabilizer is 2- 40 tert.-butyl-4-dodecyloxyphenol.

3. A stabilized composition as defined in claim 1 wherein the polymer is polyethylene and the stabilizer is 2- tert.-butyl-4-tetradecyloxyphenol.

4. A stabilized composition as defined in claim 1 wherein the polymer is polyethylene and the stabilizer is 2-tert.-butyl-4-octadecyloxyphenol.

5. A stabilized composition as defined in claim 1 wherein the polymer is polypropylene and the stabilizer is 2- tert.-butyl-4-dodecyloxyphenol.

6. A stabilized plastic composition at a temperature above C. which is normally subject to thermal oxidative deterioration consisting of a normally solid polymer selected from the group consisting of polyethylene and polypropylene and from about 0.001% to about 3% by weight of a stabilizer selected from the group consisting of those compounds having the followwherein n is an integer of from 12 to 18, inclusive.

7. A process for shaping a plastic composition con sisting of a normally solid polymer selected from the group consisting of polyethylene and polypropylene which is normally subject to thermal oxidative deterioration which comprises mixing and plasticating said polymer at a temperature of at least 140 C. with from about 0.001% to about 3% by weight of a stabilizer selected from the group consisting of those compounds having the following formulas:

on on /CH3 o-on on C-CH:

I GnHznn nHzm-r References Cited in the file of this patent UNITED STATES PATENTS Chenicek Mar. 27, 1955 Nelson et a1. May 20, 1958 

1. A STABILIZED COMPOSITION OF MATTER NORMALLY SUBJECT TO THERMAL OXIDATIVE DEGRADATION CONSISTING OF A NORMALLY SOLID POLYMER SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE AND POLYPROPYLENE AND FROM ABOUT 0.001% TO ABOUT 3% BY WEIGHT OF A STABILIZER SELECTED FROM THE GROUP CONSISTING OF THOSE COMPOUNDS HAVING THE FOLLOWING FORMULAS: 